title: High-mobility group box-1 mediates toll-like receptor 4-dependent angiogenesis.
abstract: OBJECTIVE
  Inflammation is closely linked to angiogenesis, and Toll-like receptors (TLRs) are the key mediators of inflammatory responses. However, the impact of TLRs on angiogenesis is incompletely understood. In this study, we determined the involvement of TLRs in angiogenesis.
  
  
  RESULTS
  In a mouse model of alkali-induced corneal neovascularization (CNV), we found that CNV was attenuated in TLR4-/- but not TLR2-/- mice. Further study revealed that the absence of TLR4 led to decreased production of proangiogenic factors in association with reduced accumulation of macrophages at the site of wounds, which was associated with reduced expression of high-mobility group box-1 (HMGB1) protein, an endogenous ligand for TLR4. Topical application of HMGB1 to the injured cornea promoted CNV with increased macrophage accumulation in wild-type mice but not in TLR4-/- mice. HMGB1 treatment in vitro also promoted the production of proangiogenic factors by mouse macrophages in a TLR4-dependent manner. Furthermore, antagonists of HMGB1 and TLR4 reduced CNV and macrophage recruitment in the injured cornea of wild-type mice.
  
  
  CONCLUSIONS
  Our results suggest that the release of HMGB1 in the wounds initiates TLR4-dependent responses that contribute to neovascularization. Thus, targeting HMGB1-TLR4 signaling cascade may constitute a novel therapeutic approach to angiogenesis-related diseases.
authors.affiliation: State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, 54 S Xianlie Rd, Guangzhou 510060, China.
authors.forename: Qing
authors.initials: Q
authors.lastname: Lin
authors.forename: Xiao Ping
authors.initials: XP
authors.lastname: Yang
authors.forename: Dan
authors.initials: D
authors.lastname: Fang
authors.forename: Xiangrong
authors.initials: X
authors.lastname: Ren
authors.forename: Hongyan
authors.initials: H
authors.lastname: Zhou
authors.forename: Jiazhu
authors.initials: J
authors.lastname: Fang
authors.forename: Xialin
authors.initials: X
authors.lastname: Liu
authors.forename: Shiyou
authors.initials: S
authors.lastname: Zhou
authors.forename: Feng
authors.initials: F
authors.lastname: Wen
authors.forename: Xiaohong
authors.initials: X
authors.lastname: Yao
authors.forename: Ji Ming
authors.initials: JM
authors.lastname: Wang
authors.forename: Shao Bo
authors.initials: SB
authors.lastname: Su
mesh_terms: D042501:Angiogenic Proteins / Q000378:metabolism; D000818:Animals; D002633:Chemotaxis; D003315:Cornea / Q000098:blood supply* / Q000187:drug effects / Q000378:metabolism* / Q000473:pathology; D016510:Corneal Neovascularization / Q000139:chemically induced / Q000235:genetics / Q000378:metabolism* / Q000473:pathology / Q000503:physiopathology / Q000517:prevention & control; D004195:Disease Models, Animal; D042783:Endothelial Cells / Q000378:metabolism; D005260:Female; D024243:HMGB1 Protein / Q000037:antagonists & inhibitors / Q000378:metabolism*; D008070:Lipopolysaccharides / Q000494:pharmacology; D008264:Macrophages / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D018919:Neovascularization, Physiologic / Q000187:drug effects; D010446:Peptide Fragments / Q000494:pharmacology; D015398:Signal Transduction; D012972:Sodium Hydroxide; D013997:Time Factors; D051195:Toll-Like Receptor 2 / Q000235:genetics / Q000378:metabolism; D051197:Toll-Like Receptor 4 / Q000037:antagonists & inhibitors / Q000172:deficiency / Q000235:genetics / Q000378:metabolism*
chemical_list: D042501:Angiogenic Proteins; D024243:HMGB1 Protein; D008070:Lipopolysaccharides; D010446:Peptide Fragments; C493486:Tlr2 protein, mouse; C493487:Tlr4 protein, mouse; D051195:Toll-Like Receptor 2; D051197:Toll-Like Receptor 4; D012972:Sodium Hydroxide